Certain benzo[α]phenoselenazinium compounds are known (Cancer Research 1993, Vol 53 (11), p 2571-2580) and their performance was compared with S containing analogues in use for treatment of murine sarcoma tumours in vitro, along with their ability to yield singlet oxygen. However, a compound's ability to yield singlet oxygen does not provide a reliable way to predict whether or not a compound will be effective in therapy.
For example, a study of chalcogenopyrylium dyes as potential sensitizers for the photodynamic therapy of cancer in Journal of Medicinal Chemistry (1999), 42(19), 3953-3964 concluded that the presence of a sulphur, selenium, or tellurium heteroatom in a molecule had no predictable impact on its toxicity. Further in Photochemistry and Photobiology (1998), 67(6), 612-625 the cytotoxic effects of Nile blue selenium (EtNBSe) were compared with those of Photofrin (a drug that is degraded via a 1O2-mediated mechanism) it concluded that the lower threshold 1O2 dose and the higher extinction coefficient and higher 1O2 yield for EtNBSe does not necessarily result in improved photodynamic effects.
Seleno-methylene blue and its properties as an anti-oxidant and anti-inflammatory is discussed in Agents and Actions 1993, Vol 38, C143-C145 and concludes that the selenium analogue does not exhibit a different anti-oxidant or anti-inflammatory profile versus the sulphur compound but does exhibit increased inhibitory activity of iron-induced hepatic lipid peroxidation in vitro and ex vivo.
The present invention seeks to provide biologically active phenoselenazinium compounds suitable for use in in vivo photodynamic therapy (PDT), particularly as anti-infectives and as anti-cancer agents. Further the present invention seeks to provide sterilising agents both for direct use and in combination with polymers.